$maxWidth: 540px;
@mixin MaxWidth {
    @media screen and (min-width: 540px) {
        @content;
    }
}

@mixin MaxWidth-center {
    @media screen and (min-width: 540px) {
        max-width: $maxWidth;
        left: 50%;
        transform: translateX(-50%);
    }
}

@mixin quanping {
    @media screen and (min-height: 700px) {
        @content;
    }
}

/**
 * 适配 iphone 底部安全区（指示条，配合index.html <meta name="viewport" ... />使用
 */